1. Technical Field
The invention relates to transformers, particularly to transformers for connectors.
2. Related Art
A connector is installed in an electric device for connecting an external device via a cable. However, once a cable has been connected to a connector, the connector even the electric devices connected by the cable may be damaged by transient overvoltage on the cable.
A network cord, which is a typical example of such a cable, is usually disposed outside a building without covering. Surges tend to occur on a network cord because of lightening. Such surges may cause damage to electric devices. Thus, some network connectors are equipped with a surge reduction element to prevent electric devices from being damaged by surges.
FIG. 1 is a circuit diagram of lightening protection in a conventional connector. The connector is arranged with an isolation transformer 10. The surges or electromagnetic interference (EMI) occurs at the primary winding 101 will be isolated by the isolation transformer 10 so as to prevent an electric device (not shown) connected to the secondary winding 102 from being damaged by the surges or EMI. However, the isolation transformer 10 can exclude most of the disruptive energy, but its secondary winding may still generate surges. Therefore, the electric device cannot be completely protected only by the isolation transformer.
As a result, a surge absorber 20 such as a transient voltage suppressor (TVS) must be further disposed at the two terminals 1011, 1012 of the primary winding 101 or the secondary winding 102. The surge absorber 20 can reduce overvoltage from the isolation transformer 10. However, a specific connector can be installed in various electric devices and various electric devices with different specifications usually have different safety requirements. The above-mentioned structure is disadvantageous to change of the surge absorber 20 in a connector. As a result, when the surge absorber 20 needs to be changed into another one, the only solution is to change a whole connector with a different surge absorber. Only changing the surge absorber 20 is usually unavailable. This will increase manufacturing costs.